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[gentoo-user] Do I need NUMA set up in my kernel?
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Peter Humphrey
Sep 23, 2021, 5:00:03 AM9/23/21
to
Hello list,
I see "[ 0.003162] No NUMA configuration found" in dmesg. Does that mean I
should, or can, remove the NUMA settings from the kernel? This is a Ryzen M9
5900X machine.
I have this at the moment:
$ grep NUMA /usr/src/linux/.config
CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
# CONFIG_NUMA_BALANCING is not set
CONFIG_NUMA=y
CONFIG_AMD_NUMA=y
CONFIG_X86_64_ACPI_NUMA=y
# CONFIG_NUMA_EMU is not set
CONFIG_USE_PERCPU_NUMA_NODE_ID=y
CONFIG_ACPI_NUMA=y
CONFIG_NUMA_KEEP_MEMINFO=y
--
Regards,
Peter.
I see "[ 0.003162] No NUMA configuration found" in dmesg. Does that mean I
should, or can, remove the NUMA settings from the kernel? This is a Ryzen M9
5900X machine.
I have this at the moment:
$ grep NUMA /usr/src/linux/.config
CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
# CONFIG_NUMA_BALANCING is not set
CONFIG_NUMA=y
CONFIG_AMD_NUMA=y
CONFIG_X86_64_ACPI_NUMA=y
# CONFIG_NUMA_EMU is not set
CONFIG_USE_PERCPU_NUMA_NODE_ID=y
CONFIG_ACPI_NUMA=y
CONFIG_NUMA_KEEP_MEMINFO=y
--
Regards,
Peter.
Miles Malone
Sep 23, 2021, 6:50:03 AM9/23/21
to
You'd need NUMA if you had a NUMA machine. In current context, that
would be either a) a dual socket system, b) an amd threadripper, or c)
some of the really high core xeons. If your motherboard doesnt have
certain memory banks allocated to certain processors or cores, you're
probably not running a NUMA machine.
NUMA stands for non-uniform memory access, it means that certain
processor cores have more direct access to certain parts of memory
than others do (e.g. to access the other memory they need the other
cpu core to pass it through)
On Thu, 23 Sept 2021 at 19:39, Charlotte Delenk <dark...@darkkirb.de> wrote:
>
> Hi Peter,
> Zen2) with no issues
>
>
would be either a) a dual socket system, b) an amd threadripper, or c)
some of the really high core xeons. If your motherboard doesnt have
certain memory banks allocated to certain processors or cores, you're
probably not running a NUMA machine.
NUMA stands for non-uniform memory access, it means that certain
processor cores have more direct access to certain parts of memory
than others do (e.g. to access the other memory they need the other
cpu core to pass it through)
On Thu, 23 Sept 2021 at 19:39, Charlotte Delenk <dark...@darkkirb.de> wrote:
>
> Hi Peter,
>
> On 9/23/21 10:59, Peter Humphrey wrote:
> > Hello list,
> >
> > I see "[ 0.003162] No NUMA configuration found" in dmesg. Does that mean I
> > should, or can, remove the NUMA settings from the kernel? This is a Ryzen M9
> > 5900X machine.
>
> I have CONFIG_NUMA unset on both of my AMD Ryzen machines (Zen+ and
> On 9/23/21 10:59, Peter Humphrey wrote:
> > Hello list,
> >
> > I see "[ 0.003162] No NUMA configuration found" in dmesg. Does that mean I
> > should, or can, remove the NUMA settings from the kernel? This is a Ryzen M9
> > 5900X machine.
>
> Zen2) with no issues
>
>
Peter Humphrey
Sep 23, 2021, 8:20:03 AM9/23/21
to
--
Regards,
Peter.
Peter Humphrey
Sep 23, 2021, 12:40:02 PM9/23/21
to
On Thursday, 23 September 2021 17:32:46 BST Charlotte Delenk wrote:
> On 9/23/21 18:30, Grant Taylor wrote:
> > NUMA architecture?
> >
> >
> >
> > If it will boot and run, does it simply do so in a sub-optimal way?
>
> Pure speculation for this one but if it works it's probably only going
> to detect part of the memory and some of the devices and one cpu, since
> the other resources are physically connected to the other cpus.
>
> >
> >
> > Flipping the coin on the other side, is there any negative effect
> > (other than kernel size / lines of code / attack surface) for having
> > NUMA support enabled on a non-NUMA system?
>
> There is no meaningful downside to leaving it enabled, it's enabled in
> many distribution kernels for a reason.
I've booted a kernel with no NUMA config, and it seems to run fine on this
single-socket Ryzen motherboard. I just get the one entry in dmesg:
$ dmesg | grep -i numa
[ 0.297998] pci_bus 0000:00: on NUMA node 0
That's it. I'm running five BOINC projects, some of which run on vbox, so on
this motherboard it seems clear that I don't need NUMA.
--
Regards,
Peter.
> On 9/23/21 18:30, Grant Taylor wrote:
>
> > On 9/23/21 4:39 AM, Miles Malone wrote:
> >
> >> You'd need NUMA if you had a NUMA machine. In current context, that
> >> would be either a) a dual socket system, b) an amd threadripper, or
> >> c) some of the really high core xeons. If your motherboard doesnt
> >> have certain memory banks allocated to certain processors or cores,
> >> you're probably not running a NUMA machine.
> >
> >
> >
> > Will a kernel without NUMA support boot and run on a system that has a
> > On 9/23/21 4:39 AM, Miles Malone wrote:
> >
> >> You'd need NUMA if you had a NUMA machine. In current context, that
> >> would be either a) a dual socket system, b) an amd threadripper, or
> >> c) some of the really high core xeons. If your motherboard doesnt
> >> have certain memory banks allocated to certain processors or cores,
> >> you're probably not running a NUMA machine.
> >
> >
> >
> > NUMA architecture?
> >
> >
> >
> > If it will boot and run, does it simply do so in a sub-optimal way?
>
> Pure speculation for this one but if it works it's probably only going
> to detect part of the memory and some of the devices and one cpu, since
> the other resources are physically connected to the other cpus.
>
> >
> >
> > Flipping the coin on the other side, is there any negative effect
> > (other than kernel size / lines of code / attack surface) for having
> > NUMA support enabled on a non-NUMA system?
>
> There is no meaningful downside to leaving it enabled, it's enabled in
> many distribution kernels for a reason.
I've booted a kernel with no NUMA config, and it seems to run fine on this
single-socket Ryzen motherboard. I just get the one entry in dmesg:
$ dmesg | grep -i numa
[ 0.297998] pci_bus 0000:00: on NUMA node 0
That's it. I'm running five BOINC projects, some of which run on vbox, so on
this motherboard it seems clear that I don't need NUMA.
--
Regards,
Peter.
Grant Taylor
Sep 23, 2021, 12:40:02 PM9/23/21
to
On 9/23/21 4:39 AM, Miles Malone wrote:
> You'd need NUMA if you had a NUMA machine. In current context, that
> would be either a) a dual socket system, b) an amd threadripper, or
> c) some of the really high core xeons. If your motherboard doesnt
> have certain memory banks allocated to certain processors or cores,
> you're probably not running a NUMA machine.
> would be either a) a dual socket system, b) an amd threadripper, or
> c) some of the really high core xeons. If your motherboard doesnt
> have certain memory banks allocated to certain processors or cores,
> you're probably not running a NUMA machine.
Will a kernel without NUMA support boot and run on a system that has a
NUMA architecture?
If it will boot and run, does it simply do so in a sub-optimal way?
NUMA architecture?
If it will boot and run, does it simply do so in a sub-optimal way?
Flipping the coin on the other side, is there any negative effect (other
than kernel size / lines of code / attack surface) for having NUMA
support enabled on a non-NUMA system?
--
than kernel size / lines of code / attack surface) for having NUMA
support enabled on a non-NUMA system?
Grant. . . .
unix || die
Michael
Sep 23, 2021, 2:30:03 PM9/23/21
to
On Thursday, 23 September 2021 17:38:15 BST Peter Humphrey wrote:
> I've booted a kernel with no NUMA config, and it seems to run fine on this
> single-socket Ryzen motherboard. I just get the one entry in dmesg:
>
> $ dmesg | grep -i numa
> [ 0.297998] pci_bus 0000:00: on NUMA node 0
>
> That's it. I'm running five BOINC projects, some of which run on vbox, so on
> this motherboard it seems clear that I don't need NUMA.
Out of interest, have you tried booting a NUMA enabled kernel to see what
> I've booted a kernel with no NUMA config, and it seems to run fine on this
> single-socket Ryzen motherboard. I just get the one entry in dmesg:
>
> $ dmesg | grep -i numa
> [ 0.297998] pci_bus 0000:00: on NUMA node 0
>
> That's it. I'm running five BOINC projects, some of which run on vbox, so on
> this motherboard it seems clear that I don't need NUMA.
dmesg reports? On an old laptop, which definitely has only a single AMD APU,
I get:
$ dmesg | grep -i NUMA -A2
[ 0.002078] No NUMA configuration found
[ 0.002080] Faking a node at [mem 0x0000000000000000-0x000000042effffff]
[ 0.002085] NODE_DATA(0) allocated [mem 0x42effc000-0x42effffff]
Peter Humphrey
Sep 24, 2021, 5:10:03 AM9/24/21
to
On Thursday, 23 September 2021 19:20:52 BST Michael wrote:
> Out of interest, have you tried booting a NUMA enabled kernel to see what
> dmesg reports?
Yes, it's been enabled ever since I had a dual-socket motherboard, years ago.
> Out of interest, have you tried booting a NUMA enabled kernel to see what
> dmesg reports?
I didn't understand why I did or didn't need it until I read Miles's post
yesterday (thanks, Miles). I don't know why it hadn't been made clear in any
websites I've visited.
> On an old laptop, which definitely has only a single AMD
> APU, I get:
>
> $ dmesg | grep -i NUMA -A2
> [ 0.002078] No NUMA configuration found
> [ 0.002080] Faking a node at [mem
0x0000000000000000-0x000000042effffff]
> [ 0.002085] NODE_DATA(0) allocated [mem 0x42effc000-0x42effffff]
without it I get "pci_bus 0000:00: on NUMA node 0". The system seems to run
happily either way.
--
Regards,
Peter.
Michael
Sep 24, 2021, 5:40:02 AM9/24/21
to
message was obtained *with* NUMA enabled in my kernel.
I suppose "NUMA on node 0" is the default first socket, which the kernel sets
up. If the kernel can't find a second CPU it will be 'faking' a multi-CPU
memory allocation setup, when it comes to allocate memory to the only CPU
available. If the kernel does not have NUMA enabled then it doesn't need to
fake anything. It will treat the hardware as a single socket MoBo and no
further tests would be undertaken. All suppositions of course, I haven't
looked at the code. ;-)
William Kenworthy
Sep 24, 2021, 7:30:02 AM9/24/21
to
rattus ~ # numactl --hardware
available: 1 nodes (0)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11
node 0 size: 31942 MB
node 0 free: 7210 MB
node distances:
node 0
0: 10
rattus ~ #
(Intel 6 core - NUMA emulation in the kernel.)
I can only find testing NUMA code and hardware as a reason to have
emulation enabled on a non-NUMA system?
BillK
William Kenworthy
Sep 24, 2021, 8:30:03 AM9/24/21
to
processes to particular cpu's (on an arm big.LITTLE architecture.
I will need to compile a new kernel without NUMA emulation to see if it
still works.
BillK
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